1. Field of the Invention
The present invention relates to a method of measuring luminance of an image display apparatus, a method of manufacturing the same, and a method and an apparatus for adjusting characteristics of the same, for adjusting luminance of pixels provided in the image display apparatus.
2. Description of the Related Art
In the related art, as a method of inspecting luminance of an image display apparatus, a method of inspecting pixel of a liquid crystal panel using a linear sensor is disclosed in, for example, JP-UM-A-4-055535 (Document 2). In addition, in an image display apparatus employing a surface conduction electron-emitting device (hereinafter referred to as SCE device), a method of adjusting characteristics by measuring emission luminance of a fluorescent material and applying a characteristic shifting voltage to each device is disclosed in JP-A-10-228867 (Document 1).
As shown in FIG. 2, the SCE device demonstrates non-linear characteristics for the device current If and the emission current Ie with respect to the device voltage Vf, and has a definite threshold voltage Vth for the emission current Ie.
Utilizing the characteristics described above, as shown in FIG. 11, an image display apparatus In which the SCE devices 4001 are arranged into a passive matrix by being connected in rows and columns including wiring resistances 4004, 4005 and are applied as an electron source is proposed.
When applying the multi-electron source to an image display apparatus operated by the passive matrix, suitable electric signals are applied to row wirings 4002 and column wirings 4003 for allowing a device corresponding to an arbitrary pixel to output a desired emission current. Simultaneously, a high voltage is applied to an anode electrode, not shown.
As in the case of a general timesharing driving, part of th row wirings 4002 are periodically and sequentially selected, and a selected voltage Vs is applied to a terminals of the selected row wirings 4002 and, simultaneously, a non-selected voltage Vns is applied to terminals of the non-selected row wirings 4002. Synchronously, modulating voltages Ve1-Ve6 for allowing emission current to be output according to information on images to be displayed are applied to terminals of the column wirings 4003.
Now, the voltages Ve1-Ve6, Vs, and Vns are set to suitable values so that a voltage larger than the threshold voltage Vth is applied to the selected devious and a voltage smaller than the threshold voltage Vth is applied to the non-selected devices, an mission current of a desired intensity is output only from the selected devices. Alternatively, instead of modulating the amplitude of the modulating voltage corresponding to gradation information in this manner, it is also possible to modulate the pulse duration of the modulating voltage. A operating method in combination of modulation of the amplitude of voltage and modulation of pulse duration is also applicable.
However, there is a problem in that the multi-electron source including a number of electron-emitting devices arranged may cause some variations in electron-emitting characteristics of the individual electron-emitting device due to variations in process, and thus when it is applied to a large flat image display apparatus. variations in characteristics of the respective electron-emitting devices may result in variations in luminance.
The possible reasons why the electron-emitting characteristics of the electron-emitting devices in the multi-electron source differ from each other may be various causes such as variations in component of the material used for an electron-emitting section, tolerance of dimensions and configurations of each member of the device, non-uniform energizing condition in the energization forming process, and non-uniformity in energizing conditions or ambient gas In the energization activation process.
In order to remove all these causes, highly advanced manufacturing equipment or very strict process control are required, and satisfying these requirements involves huge manufacturing costs, which is not practical.
In the document 1 described above, a method of manufacturing an image display apparatus including a step of measuring the respective characteristics and a step of applying a characteristic shifting voltage for adjusting the respective characteristics to a value corresponding to the reference value in order to remove variations is disclosed. However, it was not sufficient in the following reasons.
Measurement of the characteristics of the device required for adjusting the characteristics of the device will now be described.
In the related art, measurement of the characteristics of the d vice includes the steps of selecting a device, applying a voltage thereto, measuring the emission current Ie and luminance, and storing the results in a memory, and repeating the-above described steps for every device. When measuring luminance, adjustment of the characteristics may include adjustment of variations in light-emitting characteristics of a fluorescent material.
This process will be described further in detail referring to a flowchart in FIG. 15.
In a first place, a device is selected by a switch matrix (S1), and an amplitude data Tv is output (S2). Then a pulse signal is applied (S3), the emission current Ie is detected (S4) and the detected result is stored in the memory (S5).
Whether or not the steps from S3 to S5 has completed for every device is determined. If not, a new device is selected (S7) and the steps from S3 to S5 are performed.
When the steps were completed for every device, the Ie of all the devices are compared, and the memory voltages to be applied to the respective devices are determined (S8), the results are stored in the memory (S9). When the steps were not completed, the procedure returns to S3.
The process of measuring the characteristics of the device above has a problem in that when applied to an image display apparatus having a large number of pixels such as a high-resolution image display apparatus including a prevailing high quality TV, time period required for performing these steps increases, which results in lowering of productivity.
In addition, measurement of luminance of each pixel may result in considerable lowering of accuracy of measurement of luminance signal of the device to be measured due to the influence from the adjacent devices, such as color mixture, caused by misalignment of the fluorescent material or displacement of irradiating position of electron beams.
Furthermore, when a P22, which is a fluorescent material which is generally used in CRT is used, the duration of after-glow of the fluorescent material will be in the order of 10 μsec for green and blue, and 1 msec for red.
When measuring light emission from one device successively using an optical measuring system, considering the duration of after-glow, the interval of driving between one device and the next device must include a period corresponding to the duration of after-glow.
Therefore, when a high definition display having pixels about 1280×RGB×768 is constructed, it takes about 1000 seconds for measuring all the points.
The light-emitting characteristics of the fluorescent materials of three primary colors, that is, red fluorescent material (R), green fluorescent material (G), and blue fluorescent material (B), are Influenced by the material used or by the state in which the fluorescence material is formed, in addition to the amount of irradiation of electron corresponding to the electron-emitting characteristics of the electron-emitting device that allows the fluorescent material to emit light.
When considering white balance as a display characteristic, there may be the case in which complicated operation, such as performing adjustment of the light-emitting characteristics of the fluorescent material (the gamma characteristics which is general in CRT), or performing adjustment of the electron-emitting characteristics of the electron-emitting device to achieve the optimal white balance over the entire display unit after sensitivity of a measuring instrument is corrected, is required.
As described above, in the related art, it has taken a long time for measuring the characteristics of the respective pixels in order to adjust luminance of the pixels. In addition, accuracy of measurement was not sufficient.
Accordingly, it is an object of the present invention to provide a method of measuring luminance of an image display apparatus, a method of manufacturing the same, and a method and an apparatus for adjusting characteristics of the same, in which a time period required for measuring luminance of a pixel is reduced, and measuring accuracy is improved.